There are many different material handling systems consisting of conveyor systems and conveyor installations including more or less intelligent control for handling and transporting goods, e.g. workpieces, between different work posts in the manufacture of goods that require several work steps. In one type of material handling system, the conveyor system consists of a main conveyor, which in turn can consist of a plurality of conveyor belts, and a plurality of side conveyors. A side conveyor selectively leads workpieces from the main conveyor to work posts where one or more work steps are performed on the workpiece, after which the workpiece is returned to the main conveyor with the aid of the side conveyor.
A particular type of material handling system comprises a conveyor system in which the actual conveyor belt is placed above the work posts. The workpieces are here secured on hanging product carriers, which are moved on the main conveyor, which can be an endless conveyor belt for example. The side conveyors in this case consist of work stations which are adapted to selectively move a product carrier from the conveyor belt, which is located at an upper level, down to a work post, which is located at a lower level, with the aid of a conveyor chain. When the work step has been carried out, the product carrier is driven with the workpiece up to the conveyor belt again for continued transport of the product carrier to the next work station. Each product carrier comprises a holder in which one or more workpieces are secured. The holder is adapted to the product that is being manufactured and can hold one or more workpieces. These can be, for example, parts of a shirt, in which case the holder holds all the parts of a shirt at the start of the transport flow and in which the holder only holds the finished shirt when the product carrier reaches the end of the transport flow. Each product carrier can also comprise some form of identification means, such that the product carrier can be identified by the system, which means that each product carrier can be conveyed to predetermined work stations and onward to predetermined work posts. Such material handling systems are known to a person skilled in the art and are common particularly in the clothing industry.
The conveyor chain that conveys the product carriers from the work stations to the work posts consists of a number of articulated links, which can be carrier links and intermediate links. A carrier link can also be referred to as an inner link, and an intermediate link can also be referred to as an outer link. Each conveyor chain is driven by one or more separately controlled chain wheels. The carrier links are adapted to be able to couple to and secure a product carrier for transporting workpieces to the work post and for transporting the product carrier back to the conveyor belt after the work step has been carried out. The product carrier is preferably stopped at the work post when the work step is being carried out, without the product carrier having to be detached from the conveyor chain. If necessary, a product carrier can be released from the conveyor chain, for example for maintenance.
For the product carrier to be coupled to and uncoupled from the conveyor chain, a carrier link is designed with a retaining device in the form of a chain lock which can be opened for receiving a product carrier and closed in order to retain the product carrier. The chain lock can be opened in different ways, for example by a lever arm or by a specially adapted chain wheel.
A known carrier link, described in U.S. Pat. No. 4,817,778 A1, is provided with a spring-loaded chain lock, which is opened each time it passes an opening chain wheel, and which closes, via the spring, when it leaves the opening chain wheel. The length of the teeth of the opening chain wheel is adapted so that the teeth activate the opening function of the chain wheel, which opens the chain lock. This happens when the carrier link with the chain lock passes the opening chain wheel. The chain wheels that are intended only to advance the conveyor chain have shorter teeth, which do not come into engagement with the opening function of the chain lock. In this way, the product carrier can be easily hooked onto and unhooked from the conveyor chain at special docking and unloading stations.
In the described carrier link, the spring-loaded chain lock has a single locking tooth, i.e. it locks the product carrier only on one side. In the event of damage or wear of the chain lock or the locking tooth, this can mean that the retaining function of the chain lock does not function satisfactorily. This can in turn mean that a product carrier comes loose from the carrier link.
The single locking tooth can also be released manually in a relatively simple way, which is not always desirable. In some manufacturing, for example where traceability is desired, a product carrier should only be released by special personnel, for example for maintenance, for repair or for modifications to the work flow. In these cases, it is desirable to make the release of a product carrier relatively difficult, for example by means of a special tool key having to be used.
The described carrier link is designed for relatively light workpieces, for example shirts. In order to increase the range of use, it is desirable that the carrier link is also designed to be able to transport heavier workpieces.
The described conveyor chain functions satisfactorily in some applications, but there is room for development in order to satisfy future requirements.